SANAA, Sept 10 (Reuters) - An eight-year-old Yemeni girl died of internal bleeding on her wedding night after marrying a man five times her age, a social activist and two local residents said, in a case that has caused an outcry in the media and revived debate about child brides.

Arwa Othman, head of Yemen House of Folklore and a leading rights campaigner, said the girl, identified only as Rawan, was married to a 40-year-old man late last week in the town of Meedi in Hajjah province in northwestern Yemen.

"On the wedding night and after intercourse, she suffered from bleeding and uterine rupture which caused her death," Othman told Reuters. "They took her to a clinic but the medics couldn't save her life."

Othman said authorities had not taken any action against the girl's family or her husband.

A local security official in the provincial town of Haradh denied any such incident had taken place. He did not want to be identified because he was not authorised to speak to the press.

But two Meedi residents contacted by Reuters confirmed the incident and said that local tribal chiefs had tried to cover up the incident when news first broke, warning a local journalist against covering the story.

Many poor families in Yemen marry off young daughters to save on the costs of bringing up a child and earn extra money from the dowry given to the girl.

A U.N. report released in January revealed the extent of the country's poverty, saying that 10.5 million of Yemen's 24 million people lacked sufficient food supplies, and 13 million had no access to safe water and basic sanitation.

Human Rights Watch urged Yemen's government in December 2011 to ban marriages of girls under the age of 18, warning it deprived child brides of education and harmed their health.

Quoting United Nations and government data, HRW said nearly 14 percent of Yemeni girls were married before the age of 15 and 52 percent before the age of 18. The group said many Yemeni child brides-to-be are kept from school when they reach puberty.

Discussions on the issue were shelved by political turmoil following protests against President Ali Abdullah Saleh in 2011 that led to his ouster. (Reporting by Mohammed Ghobari; Writing by Mahmoud Habboush; editing by Mike Collett-White)